AC fan noise in dash

[tn52]

Hi everyone,
I have fan noise from somewhere in the middle of the dash when I have the AC on. It never shows up when I mentioned it to the SA at the dealer. Since they can't find it then they will not fix it. I noticed that the fan noise comes only when I use the AC, never without AC. It is very irritating on long trip because you can hear it quite loud with the AC cycling on/off.
Car is 2006 S500. Any suggestions for what to fix? Thanks.

[Klaus9000]

I was told by my SA that the entire dash needs to be disassembled to get to the "air box" and fans. A very time consuming job invloving several hours of labor but your car is probably still under warranty.

When I have issues like this (I see a problem, Dealer says they can't find it), I ask to go for a drive with the SA or Shop Foreman. It has worked every time since you can point out exactly what it is during the test drive.

Good luck!

[tn52]

Thanks for a quick reply. I would like to add that I did a couple test drives with the SA and my car did not show any AC fan noise. The noise is more likely to show up on long trips (4-5 hrs) and if it does, then it is quite loud. I can turn off the AC for a few minutes and when the AC was turned back on, it will be good for another hour or two... I just don't know how many fans do we have in the dash or just one? Obviously, it is not a common problem.

[Lucian Girbaciu]

Hi,
It can be the ambiental sensor fan what you hear, the noise can be from the dust that is covering the sensor, we usualy celean the sensor and the problem is solved but this is the procedure at Renault, Honda, and Peugeot.

[ackee911]

Had the same problem, turned out to be the AC compressor or something like that-its located under the dash on the passenger side. (I'm RHD).
Worked for me

[Skylaw]

The ambient air sensor that Lucian was talking about above is called the aspirator motor, a tiny fan motor that blows air past the cabin temperature sensors. One is located in the passenger side A/C control panel, and the other in the overhead panel (where your overhead lights and moon roof control are). They are behind small grilles.

The location from which the noise is coming can be very confusing to the driver. I would have these checked, with a stethoscope if necessary, before tearing the dashboard apart.

[gmund]

Originally Posted by Skylaw

The ambient air sensor that Lucian was talking about above is called the aspirator motor, a tiny fan motor that blows air past the cabin temperature sensors. One is located in the passenger side A/C control panel, and the other in the overhead panel (where your overhead lights and moon roof control are). They are behind small grilles.

The location from which the noise is coming can be very confusing to the driver. I would have these checked, with a stethoscope if necessary, before tearing the dashboard apart.

According to my service advisor, the electronic buzzing I hear in my dash is from the aspirator motor. Said it was normal, which to me seems strange to have this noise on an $80,000.00 car.

[Skylaw]

I do not believe it is "normal" unless your hearing is especially sensitive. I don't hear mine at all, ever. They can be replaced - unfortunately, MB no longer sells the aspirator motors themselves; they come as part of more expensive assemblies. If you still have any warranty left, make them fix it.